special characters in German disappear

I have a problem. I made my site in mobirise. no external editor used. nothing changed. then, when I try it out in browser all characters are shown. when I export the site via FTP all browsers don-t show the special characters. instead of Ä there is a Ã¤ and so on. I tested several fonts but everywhere the same. charset is on UTF 8.what is going wrong ?